Advanced Valve Train Technology
For Kart & Jr. Dragster Racing

All Go-Parts™ camshafts and engine components have been aggressively developed on the dynamometer and on the race track to provide you with the most competitive products on the market.Before building your hi-performance 5 HP Briggs and Stratton™ engine, we recommend that you read these instructions completely to familiarize yourself with the necessary tools and the preparing a high quality racing engine. We also recommend you have a copy of the Briggs and Stratton™ factory service manual for reference purposes. Use of hi-performance engine components will not improve your racing chassis handling. The quality of your chassis handling is as important as the quality of your engine.If you have any questions concerning installation or proper use of your Go-Parts™ hi-performance components, call us toll-free at 1-800-976-9376.
Go-Parts™ Complete Engine Disassembly Instructions For Briggs & Stratton™ 5 HP Engines
Remember that your goal is a hi-performance racing engine, it is in your best interest to follow these instructions precisely. Clearancing issues are dealt with and should not be ignored. Skipping steps will reduce horsepower, efficiency, and the performance of your engine.
DISASSEMBLY:Step 1 - Warm the engine at an idle. Shut the engine off and remove the blower housing, spark plug and attached hardware. Next, perform a leak down test on your engine to test the sealing condition of the engine. You can perform a leak down test while the engine is on the chassis or on the bench. Either way, you must be certain that the engine is warm, that the flywheel is held stationary during the leak down test and that both valves are closed. The flywheel can be held stationary by attaching a flywheel holding tool onto the flywheel. If the leak down test indicates a leak percentage higher than 10%, you will need to inspect and possibly repair the valve seats, head, head gasket and piston rings. If you listen closely to the engine during the leak test, you can pinpoint the source of the leakage. Overlooking the sealing condition of your engine can cause inaccurate performance potential from your new camshaft.
Tip: Go-Parts™ offers a leak down tester (part #GP301010) that is an accurate and dependable tool for this application.
Step 2: Remove clutch, clutch guard, header, straps, carburetor, tank, all hardware and brackets. When removing these components, check the condition of the fasteners and engine block threads. Replace or repair if necessary.Step 3: Drain fuel and oil/lubricant and dispose of properly.Step 4: Remove the cylinder head and valve cover. Remove valve springs and valves. When removing dual valve springs, use Go-Parts™ Dual Valve Spring Compressor (part #GP351018) for safety and ease. Stock class springs can be removed with a stock spring compressor or two screwdrivers. Inspect valves, retainers, valve guides and valve seats for wear. Replace or repair if necessary.
In stock classes, replace stock valve springs every three to four races.
If using Go-Parts™ dual springs in modified classes, replacement is necessary every eight to ten races.
For stock classes, check the Go-Parts™ application sheet for the proper valve spring for your camshaft.
For modified classes, check the Go-Parts™ application sheet for the proper spring for your cam. Go-Parts™ offers two different dual valve spring sizes to fit all modified engines. Part #GP959-Kit is designed for use on modified engines with camshaft lifts up to .380". Part #GP960-Kit is designed for use on modified engines with cam lifts over .380".
Step 5: Remove the side cover and side cover gasket from the engine. Remove PTO bearing. PTO bearing should be a slip-fit.
If PTO bearing is not slip-fit, you will need to completely disassemble the engine to install your new camshaft or use a "puller" to remove the PTO bearing.
If you use a "puller" to remove the PTO bearing, you must have the crankshaft journal "turned down" to allow the PTO bearing to slip-fit upon reassembly AND must replace the PTO bearing.
If your engine is not equipped with a PTO bearing, you must inspect the clearance between the bushing inside diameter and the crankshaft journal outside diameter.
If clearance is excessive or bushing quality is poor, replace crankshaft and/or repair bushings.

Note: If you choose to leave the PTO bearing pressed on the crankshaft, you will have to remove the piston and connecting rod; remove the crankshaft and camshaft; and reinstall the crankshaft simultaneously with the new camshaft.
Step 6: Turn the engine upside down or deck surface down, line up the crankshaft and camshaft timing marking dots and remove the camshaft. When removing the camshaft be careful not to "knick" the camshaft lobes on any internal engine components.INSPECTION:Step 7 - Remove and inspect the lifters for wear pattern.
If your engine is a modified class engine, we highly recommend replacing your lifters with stronger & harder Go-Parts™ lifters regardless of the existence of any wear patterns.
If your engine is a stocker or restricted stocker, and has had a "fast-rapid" lift or a "fast-ramp" camshaft previously, you must install new lifters.
Use Go-Parts™ Billet stock class lifters (GP8250-2), which will allow the cam to "degree in" every time. These lifters will also pass tech inspection.
Fast lift camshafts have been known to break weaker lifters, valve spring retainers, valve guides and consequently ruining some engine blocks. Overlooking this fact can cause severe engine damage.

Inspect for excessive clearance in the lifter bore. If the lifter appears loose in the lifter bore, installing a sleeve in the lifter bore area may be necessary. It will also be necessary for you to inspect the quality of the valve guide bore. If excessive clearance is present, you will have to replace the valve guide. If you install a new valve guide, you will need to "lap" the valve or cut the valve seat with the proper seat valve cutter.

Note: All valve lapping and seat cutting should be performed with a "torque-plate" attached to the top of the block and torqued to spec.

Note: If you are not familiar with the type of camshaft that you are removing, replace the lifters for safety.

Note: Check sanctioning body legality before cutting valve seats.

Note: If reusing a lifter, make sure to mark the lifter during disassembly and reinstall the same lifter in the same lifter bore originally installed in.

Note: Inspect the entire valve train for faulty components and for faulty valve sealing. Installing a new camshaft without inspecting the quality of all internal components may lead to poor performance and possibly engine failure.
Step 8: In modified class engines you must now inspect for proper internal components-to-crankcase clearances.
The main areas to inspect are:
1. Connecting rod to camshaft intake lobe clearance.
2. Connecting rod to camshaft "barrel" (area between lobes) clearance.
3. Camshaft to crankshaft clearance.
4. Connecting rod to crankshaft clearance.
5. Lifter head to lifter bore clearance at max. lift.

It may be necessary to remove material from the bottom of the lifter bore, the camshaft "barrel" (center section between both camshaft lobes), the sides of the camshafts lobes, the crankshaft "pin" area and the connecting rod. A .030 clearance between internal components is acceptable. Clean engine parts with a clean cloth. Install (with a light film of oil) the crankshaft, camshaft, piston (with no piston rings) on the connecting rod, lifters and PTO bearing. Be sure to line up the timing marks on the crank gear and the camshaft. Turn the engine over very slowly and with a flash light, look through the Go-Parts™ billet camshaft gear face and view where material needs to be removed from the engine block or any internal engine components. After removing the necessary amount of material and cleaning all parts, recheck the tolerances with crankcase cover and crankcase cover gasket installed and torqued. This can be done by listening closely for internal noise while you are slowly turning the engine over in the direction of rotation.

Note: It may be necessary to hold finger pressure down on the lifters while checking for internal clearances. See Go-Parts™ lifter installation instructions for further details.

Note: Firing and running the engine without checking clearances can be fatal to engine life.

Note: Go-Parts™ billet modified camshaft installation numbers match the cam card when the cam gear tooth marked as "0" lines up with the crank gear marking dot (as shipped). If you change the location of the cam gear to the crank gear by advancing or retarding the cam gear on the camshaft, you will need to re-check clearances before running again.
You are now be ready for re-assembly.If you have any questions, call us toll-free at 1-800-976-9376 for assistance.